And on, on and on, and on we goAnd on, on and on, and on we goWe love what we had, but now it’s goneLet’s leave before we eat each other aliveAlive

Macklemore is saying that they go on in their dysfunctional relationship but while they used to love each other and their relationship, that love is gone. They need to breakup before they “eat each other alive” meaning before they completely tear each other apart.